TWI535331B - Light emitting diode protection circuit - Google Patents

Description

Light-emitting diode protection circuit

The invention relates to a light-emitting diode protection circuit, in particular to an over voltage protection (OVP) and an over current protection (OCC) for a light-emitting diode by using a fuse element and a discharge protection element. ), over temperature protection (OTP) and lightning protection (Lightning Protection) and other multifunctional protection circuits.

The price of oil in the world is rising day by day. The supply of energy and raw materials has become the most important issue. How to save electricity and save consumables is a key goal of industrial technology. Lighting equipment, which accounts for a large proportion of energy consumption, has become an important energy-saving. project. At present, LEDs have many advantages over traditional incandescent bulbs and fluorescent tubes, such as small size (multiple, multiple combinations), low heat generation (less heat radiation), low power consumption (low voltage, low) Current start), long life (100,000 hours or more), fast response (high frequency operation), environmental protection (shockproof, impact resistant, non-destructive, waste-recyclable, non-polluting), flat package and easy to develop into light and short The advantages of the product. Therefore, as the brightness of the light-emitting diode increases and the cost decreases, the use of the light-emitting diode increases, for example, it is widely used in white light illumination devices, indicator lights, vehicle signal lights, automotive headlights, flash lamps, and liquid crystal displays. The backlight module, the light source of the projector, the outdoor display unit, and the like.

At present, most of the electrical and electronic products provide power from the mains. Most of them contain electrical conductors such as metals for power transmission. Therefore, lightning strikes may be very large. In addition to high currents, high voltages are often caused by lightning. The main cause of damage to electrical or electronic products. Taking the light-emitting diode product as an example, the light-emitting diode product is driven by AC (commercial power), and it is easy to have a large current generated by an instantaneous high voltage (surge) during driving, thereby injuring the AC light-emitting diode and causing damage. Or shortened life. Therefore, how to avoid the damage of the LED products from overcurrent, overvoltage, surge, lightning strike and other factors.

In view of the above, the present invention has been directed to the absence of the prior art described above, and proposes a light-emitting diode protection circuit to effectively overcome the above problems.

The main object of the present invention is to provide a light-emitting diode protection circuit, which can effectively avoid damage of a product caused by factors such as overvoltage, overcurrent, over-temperature or lightning strike of a circuit of a light-emitting diode, thereby improving the product. Reliability and service life.

To achieve the above objective, the present invention provides a light-emitting diode protection circuit including a light-emitting diode module; two fuse elements respectively connected to the light-emitting diode module, and the current flowing through the fuse element exceeds a protection current When the value is, the system is in an open state to cut off a large current flowing through the light emitting diode module; and a discharge protection component is connected to the light emitting diode module, the second first fuse element, and the discharge protection component provides illumination One of the diode modules is a current bypass path.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

The LED protection circuit of the invention can operate under the AC power source and the DC power source, and can avoid overcurrent, overvoltage, over temperature and surge or lightning strike caused by operating under the AC power source and the DC power source. The damage is first described as an example of operating under a DC power supply. As shown in FIG. 1 , the first embodiment of the present invention operating under a DC power supply is applied to LED illumination, backlight display, and the like. A light-emitting diode protection circuit for an electronic device. The LED protection circuit includes a light emitting diode module 10 and two fuse elements, which are a first fuse element 12 and a second fuse element 14, and a discharge protection element 16.

The LED module 10 includes a plurality of LEDs (LEDs) to form a light-emitting diode string or a plurality of LED strings in parallel. The two ends of the first fuse element 12 are respectively connected to the positive voltage end of the DC power source and the anode of the LED module 10; the two ends of the second fuse element 14 are respectively connected to the negative voltage terminal of the DC power source and the LED module. The anode of the group 10, wherein the first fuse element 12 and the second fuse element 14 are preferably double-core electronic fuses, also known as polymer polymer positive temperature thermistors (PTC), which are composed of polymers and conductive particles. The conductive particles form a chain-like conductive path in the polymer after special processing. The two ends of the discharge protection component 16 are respectively connected to a positive voltage terminal and a negative voltage terminal of the DC power source.

When the normal operating current passes through the first fuse element 12 and the second fuse element 14, the extremely low impedance value can be maintained to cause the LED module 10 to operate normally. When both the overcurrent and the overvoltage occur simultaneously or in either case, the first fuse element 12 and the second fuse element 14 generate heat (energy E) due to the relationship between current and resistance (I ² R) when current flows. = current I × voltage V), and the generated heat will be completely or partially diverged into the environment; in other words, when a large current flows through the first fuse element 12 and exceeds a protection current value, the first fuse element 12 generates The heat will be greater than the divergence, that is, the protection state is activated, and the system is in an open state, so that a large current is cut off through the light-emitting diode module 10, that is, the heat generated by the large current causes the polymer to rapidly expand. The conductive path formed by the conductive particles is cut off, and the double-type electronic fuse is in a high-resistance state (open state) to achieve the effect of the light-emitting diode module 10 from being damaged. The utility model has the advantages of using the multiplexable electronic fuse: when the overcurrent (overtemperature state) disappears in the circuit, the polymer cools and the volume returns to normal, wherein the conductive particles reconstitute the conductive path and assume an initial low resistance state. continue to use.

In addition, when a surge or lightning strike occurs, the large current generated by the instantaneous high voltage will directly enter the positive voltage end of the DC power supply (such as the phenomenon of a positive lightning strike), or the negative voltage end of the DC power supply from the ground end ( If a negative lightning strike occurs, the two ends of the discharge protection component 16 are respectively connected to the positive voltage terminal and the negative voltage terminal of the DC power supply, and when the discharge protection component 16 is not activated, it is in a high resistance state, and when an overvoltage occurs, It can be converted into a low-resistance state in an instant, so as a large current discharge path, a current bypass path of the light-emitting diode module 10 is provided, so that the perfect protection of the LED module 10 can be achieved. The discharge protection component 16 is preferably a micro discharge tube (BLSA), which combines the advantages of a ceramic gas discharge tube and a semiconductor overvoltage protector: high insulation resistance, small interelectrode capacitance, and large discharge current (up to 3 kA). ), two-way symmetry, fast response (no hysteresis of impact breakdown), stable and reliable performance, low voltage after conduction, high DC breakdown voltage (up to 5000V), small size, long life, etc. advantage.

As shown in FIG. 2, the second embodiment of the present invention operates under a DC power supply, and the difference from FIG. 1 is only that the connection manner of the discharge protection element 16 is different. Therefore, the differences may be explained here. Referring to the first embodiment of Fig. 1, no further details are provided herein. The difference between the second embodiment and the first embodiment is that one end of the discharge protection element 16 is connected between the first fuse element 12 and the anode of the LED module 10, and the other end is connected to the negative voltage end of the DC power supply. . The purpose is that when a phenomenon of forward lightning strike occurs, a large current generated by the instantaneous high voltage flows through the first fuse element 12, and since the current flowing through the first fuse element 12 is greater than the protection current value, the protection state is activated, because The resistance value of the first fuse element 12 is relatively sensitive to the temperature change, and the high temperature caused by the large current causes the resistance value to instantaneously jump to a high resistance state, directly limiting the large current to the light emitting diode module 10, The input voltage is protected within a voltage range that the LED module 10 can withstand. In addition, if the instantaneous high voltage generated by the forward lightning strike causes the first fuse element 12 to start the protection, it passes through the path of the LED module 10, and the large current portion can be directly discharged by the discharge protection component 16. The discharge is performed, and a part is directly introduced to the ground, which can effectively absorb the high voltage generated in the circuit.

Further, as shown in FIG. 3, the third embodiment of the present invention operates under a DC power supply, and the difference from the first figure is only that the connection manner of the discharge protection element 16 is different, so the difference point may be explained here. Referring to the first embodiment of FIG. 1, it will not be repeated here. The third embodiment differs from the first embodiment in that one end of the discharge protection element 16 is connected between the first fuse element 12 and the anode of the LED module 10, and the other end is connected to the second fuse element 14. Between the negative electrode of the LED module 10. When a positive or negative lightning strike occurs, the large current generated by the instantaneous high voltage directly enters the positive voltage terminal or the negative voltage terminal of the DC power source. At this time, the current flows through the first fuse element 12 or the second fuse element 14. It is greater than the protection current value, that is, the protection state is activated. For example, when a forward lightning strike occurs, the first fuse element 12 is in an open state, and is performed by the discharge protection element 16 unless the reaction speed of the first fuse element 12 is less than the high current instantaneous feed speed and the protection action is not activated. The large current is discharged, and the remaining weak current flows through the second fuse element 14 to dissipate the heat generated by the environment, so as to prevent the LED module 10 from being damaged by overvoltage or overcurrent. When a negative lightning strike occurs, the second fuse element 14 is in an open state, and unless the reaction speed of the second fuse element 14 is less than the high current instantaneous feed speed and the protection operation is not activated, the discharge protection element 16 performs a large current discharge. The remaining weak current flows through the first fuse element 12, and the heat generated by the first fuse element 12 is dissipated in the environment, so as to prevent the LED module 10 from being damaged by overvoltage or overcurrent.

The first fuse element 12 operating under the DC power supply can also use a general fuse. The purpose is that when the double-type electronic fuse uses the negative temperature, the overcurrent protection increases with the temperature, so the performance is poor, so the general fuse can be used. Compensate for the lack of characteristics of the detachable electronic fuse at negative temperature.

Next, the embodiment of the present invention operating under an AC power source is further illustrated. As shown in FIG. 4, the fourth embodiment of the present invention operates under an AC power source, and is applied to LED illumination, backlight display, and the like. A light-emitting diode protection circuit for an electronic device. The LED protection circuit includes a light emitting diode module 10 and two fuse elements, which are a first fuse element 12 and a second fuse element 14, and a discharge protection element 16. The LED module 10 includes a plurality of serially connected first polarity light emitting diodes 18 and a plurality of serially connected second polarity light emitting diodes 20, and the first polarity light emitting diodes 18 and the like The polarities of the dipolar light-emitting diodes 20 are opposite. The two ends of the first fuse element 12 are respectively connected with a positive voltage reference point of the AC power source and the LED module 10, and the two ends of the second fuse element 14 are respectively connected to the negative voltage terminal of the AC power source and the LED module. The two ends of the discharge protection component 16 are respectively connected to a positive voltage reference point and a negative voltage terminal of the AC power source.

Hereinbefore, the embodiment in which the circuit is in a normal operating state is described. When the positive voltage reference point of the alternating current input is positive and the normal operating current is current, the current sequentially passes through the first fuse element 12 and the light emitting diode. The first polarity light-emitting diodes 18 of the module 10, the first fuse element 12 is maintained at a very low impedance value, so that the first polarity light-emitting diodes 18 are normally operated (normal lighting). When the positive voltage reference point of the alternating current input is in the negative direction and is the normal working current, the current sequentially passes through the second fuse element. 14 and the second polarity LEDs 20 of the LED module 10, the second fuse element 14 maintains a very low impedance value at this time, so that the second polarity LEDs 20 can operate normally.

In other words, when both the overcurrent and the overvoltage occur simultaneously or in either case, since the AC power source alternately drives the first polarity light emitting diodes 18 and the second polarity light emitting diodes 20, the first When the fuse element 12 and the second fuse element 14 flow at a large current and exceed a protection current value, the heat generated by the first fuse element 12 and the second fuse element 14 is greater than the divergence, and the protection is respectively activated. The state is an open circuit state, according to which a large current is cut off through the light emitting diode module 10, please refer to FIG. 5 at the same time, which is an oscilloscope waveform diagram measured after the overcurrent protection of the present invention, according to which the light emission is achieved. The polar body module 10 is protected from damage. When the overcurrent disappears in the circuit, the first fuse element 12 and the second fuse element 14 are in an initial low resistance state, and continue to serve as a protection function for overvoltage and overcurrent.

In addition, when a surge or lightning strike occurs, the large current generated by the instantaneous high voltage will directly enter the positive reference voltage point of the AC power supply (such as the phenomenon of a positive lightning strike), or the negative voltage terminal of the AC power supply from the ground end. (In the case of a negative lightning strike), since both ends of the discharge protection component 16 are respectively connected to the positive voltage reference point and the negative voltage terminal of the AC power source, when the discharge protection component 16 is not activated, it is in a high resistance state, and when an overvoltage occurs In time, it can be converted into a low-resistance state in an instant, so as a large-current discharge path, a current bypass path of the light-emitting diode module 10 is provided, please refer to FIG. 6 at the same time, which is the overvoltage protection of the present invention. The measured oscilloscope waveform diagram can be seen from the figure. After the discharge protection component 16 performs current discharge, the current tends to zero, so that the perfect protection of the LED module 10 can be achieved.

As shown in FIG. 7, the fifth embodiment of the present invention operates under an alternating current power supply, and the difference from the fourth embodiment is only that the connection manner of the discharge protection element 16 is different, so the difference point may be explained here. Referring to the fourth embodiment of Fig. 4, no further details are provided herein. The fifth embodiment differs from the fourth embodiment in that one end of the discharge protection element 16 is connected between the first fuse element 12 and the LED module 10, and the other end is connected to the negative voltage terminal of the AC power source. The purpose is to: when the phenomenon of forward lightning strike occurs, the instantaneous high voltage is produced. The generated large current flows through the first fuse element 12. Since the current flowing through the first fuse element 12 is greater than the protection current value, the protection state is activated, and the resistance value instantaneously bounces to a high resistance state, directly limiting the large current. Flowing to the first polarity light-emitting diodes 18 of the LED module 10; at this time, the second polarity LEDs 20 will operate due to the current flowing therein, and then the overcurrent in the circuit After the disappearance, the first polarity LEDs 18 and the second polarity LEDs 20 are alternately driven by the AC power source, thereby effectively protecting the input voltage from the voltage range that the LED module 10 can withstand. Inside. In addition, if the instantaneous high voltage generated by the forward lightning strike causes the first fuse element 12 to start the protection, it passes through the path of the LED module 10, and the large current portion can be directly discharged by the discharge protection component 16. The discharge is performed, and a part is directly introduced to the ground, which can effectively absorb the high voltage generated in the circuit.

Further, as shown in FIG. 8, the sixth embodiment of the present invention operates under an alternating current power supply, and the difference from the fourth embodiment is only that the connection manner of the discharge protection element 16 is different, so the difference point may be explained here. Referring to the fourth embodiment of FIG. 4, details are not described herein again. The difference between the sixth embodiment and the fourth embodiment is that one end of the discharge protection element 16 is connected between the first fuse element 12 and the LED module 10, and the other end is connected to the second fuse element 14 and emits light. Between the diode modules 10 . When a positive or negative lightning strike occurs, the large current generated by the instantaneous high voltage directly enters the positive reference voltage point or the negative voltage terminal of the DC power supply. At this time, the first fuse element 12 or the second fuse element 14 flows through. The current is greater than the protection current value, that is, the protection state is activated. For example, when a forward lightning strike occurs, the first fuse element 12 is in an open state, and is performed by the discharge protection element 16 unless the reaction speed of the first fuse element 12 is less than the high current instantaneous feed speed and the protection action is not activated. The large current is discharged, and the remaining weak current flows through the second fuse element 14 to dissipate the heat generated by the environment, so as to prevent the LED module 10 from being damaged by overvoltage or overcurrent. When a negative lightning strike occurs, the second fuse element 14 is in an open state, and unless the reaction speed of the second fuse element 14 is less than the high current instantaneous feed speed and the protection operation is not activated, the discharge protection element 16 performs a large current discharge. The remaining weak current flows through the first fuse element 12, and the heat generated by it is dissipated in the environment to avoid illuminating The diode module 10 is damaged by overvoltage or overcurrent.

In summary, the present invention utilizes a fuse element and a discharge protection element to implement a multi-function protection circuit for overvoltage, overcurrent, overtemperature, and lightning strike protection of the LED.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, any changes or modifications of the features and spirits of the present invention should be included in the scope of the present invention.

10‧‧‧Lighting diode module

12‧‧‧First fuse element

14‧‧‧Second fuse element

16‧‧‧Discharge protection components

18‧‧‧First Polar Light Emitting Diode

20‧‧‧Second polarity light-emitting diode

Figure 1 is a first embodiment of the present invention operating under a DC power supply.

Figure 2 is a second embodiment of the present invention operating under a DC power source.

Figure 3 is a third embodiment of the present invention operating under a DC power source.

Figure 4 is a fourth embodiment of the present invention operating under AC power.

Figure 5 is a waveform diagram of the oscilloscope measured after the overcurrent protection of the present invention.

Figure 6 is a waveform diagram of the oscilloscope measured after the overvoltage protection of the present invention.

Figure 7 is a fifth embodiment of the present invention operating under AC power.

Figure 8 is a sixth embodiment of the present invention operating under AC power.

10. . . Light-emitting diode module

12. . . First fuse element

14. . . Second fuse element

16. . . Discharge protection component

Claims (8)

A light-emitting diode protection circuit comprising: a light-emitting diode module; and two fuse elements respectively connected to the light-emitting diode module, wherein the current flowing through the fuse element exceeds a protection current value a state in which a large current flows through the light emitting diode module, and after the current disappears, the fuse element is in an initial low resistance state, and the two fuse elements are double-core electronic fuses; and a discharge a protective component, which is a micro-discharge tube, is connected to the LED module and the two fuse elements. When an overvoltage occurs, the discharge protection component is converted into a low-resistance state, and the LED module is provided. A current bypass path, and after the discharge protection element performs a large current discharge, the current tends to zero. The light-emitting diode protection circuit of claim 1, wherein the two fuse elements are a first fuse element and a second fuse element, and the two ends of the first fuse element are respectively connected to a DC power source. a positive voltage terminal and a positive pole of the light emitting diode module, wherein two ends of the second fuse element are respectively connected to a negative voltage end of the DC power source and a negative electrode of the LED module, and the two ends of the discharge protection component are respectively The positive voltage terminal and the negative voltage terminal of the DC power source are connected. The light-emitting diode protection circuit of claim 2, wherein one end of the discharge protection element is connected between the first fuse element and the positive electrode of the light-emitting diode module, and the other end is connected. The negative voltage terminal of the DC power source. The light-emitting diode protection circuit of claim 2, wherein one end of the discharge protection element is connected between the first fuse element and the positive electrode of the light-emitting diode module, and the other end is connected. Between the second fuse element and the negative electrode of the LED module. The illuminating diode protection circuit of claim 1, wherein the illuminating diode module comprises a plurality of first polarity illuminating diodes and a second polarity illuminating unit when operating under an alternating current power source. a diode, and the first polarity light emitting diodes are opposite in polarity to the second polarity light emitting diodes. The light-emitting diode protection circuit of claim 1, wherein the two fuse elements are a first fuse element and a second fuse element, and the two ends of the first fuse element are respectively connected to an AC power source. a positive voltage reference point and the light emitting diode module, wherein two ends of the second fuse element are respectively connected to a negative voltage end of the alternating current power source and the light emitting diode module, and the two ends of the discharge protection component are respectively connected to the alternating current The positive voltage reference point of the power supply and the negative voltage terminal. The light-emitting diode protection circuit of claim 6, wherein one end of the discharge protection element is connected between the first fuse element and the LED module, and the other end is connected to the AC power source. The negative voltage terminal. The light-emitting diode protection circuit of claim 6, wherein one end of the discharge protection element is connected between the first fuse element and the light-emitting diode module, and the other end is connected to the first Between the two fuse elements and the light emitting diode module.